Simpsonian 'Evolution by Jumps' in an Adaptive Radiation of Anolis Lizards

TL;DR

This study provides evidence that Anolis lizards have evolved through significant evolutionary jumps, supporting Simpson's hypothesis that species enter new adaptive zones via key traits or dispersal, with jumps linked to habitat shifts.

Contribution

The paper introduces a novel statistical method to test Simpson's hypothesis and demonstrates that adaptive shifts in Anolis lizards occur through evolutionary jumps.

Findings

Anoles evolved via evolutionary jumps in trait development.

Jumps are associated with habitat specialization and dispersal.

Major adaptive shifts coincide with key trait evolution.

Abstract

In his highly influential view of evolution, G. G. Simpson hypothesized that clades of species evolve in adaptive zones, defined as collections of niches occupied by species with similar traits and patterns of habitat use. Simpson hypothesized that species enter new adaptive zones in one of three ways: extinction of competitor species, dispersal to a new geographic region, or the evolution of a key trait that allows species to exploit resources in a new way. However, direct tests of Simpson's hypotheses for the entry into new adaptive zones remain elusive. Here we evaluate the fit of a Simpsonian model of jumps between adaptive zones to phylogenetic comparative data. We use a novel statistical approach to show that anoles, a well-studied adaptive radiation of Caribbean lizards, have evolved by a series of evolutionary jumps in trait evolution. Furthermore, as Simpson predicted, trait axes strongly tied to habitat specialization show jumps that correspond with the evolution of key traits and/or dispersal between islands in the Greater Antilles. We conclude that jumps are commonly associated with major adaptive shifts in the evolutionary radiation of anoles.